An asylum seeker arrested as part of an Italian counter-terror and human trafficking operation may have travelled around the UK scouting potential targets, reports suggest.

Hakim Nasiri, from Afghanistan, was detained with two other men after pictures of potential targets in London, Paris and Rome were found on mobiles.

An airport, port and shopping mall are feared to have been on a possible hit list drawn up by a group "making preparations", according to Italian prosecutors.

The 23-year-old posted pictures online of himself outside Buckingham Palace and at the Shard, the Daily Mail said, adding that he also claimed to be a student and the manager of a takeaway in Birmingham.

The paper quoted Vincenzo Molinese, a colonel in the Bari military police, saying images found on Nasiri's phone of him apparently holding a machine gun " were probably taken in the back room of a supermarket in England".

Other photos reportedly found on a Facebook profile showed Nasiri posing in the Star City shopping centre, Birmingham, and travelling on a train through south-east London.

Nasiri was arrested at a home for asylum seekers in Bari on Wednesday. He is understood to have been held on suspicion of subversive association with the goal of international terrorism.

Two other men, Afghan Gulistan Ahmadzai, 29, and Pakistani Zulfiqar Amjad, 24, who were arrested in Milan on suspicion of aiding illegal immigration, had obtained international protection status in Italy.

Two more suspects are thought to have returned to Afghanistan.

At a news conference on Tuesday, prosecutor Roberto Rossi said there was no evidence an attack was imminent, but added: "It is clear they were making preparations."

Analysis of phones seized from five men found filming in a shopping centre in Bari in December uncovered photos of sites in London, Paris and Rome, as well as images showing "ideological hatred of the West and support for terrorism in Afghanistan", prosecutors said.

They reportedly included images of disfigured US soldiers and dead British troops being repatriated.

Among the images on the mobile phones were sites and hotels in London's Docklands and the Westfield shopping centre in Stratford.